The use of standardized uptake values for assessing FDG uptake with PET in oncology: a clinical perspective

Deep learning generation of preclinical positron emission tomography (PET) images from low-count PET with task-based performance assessment

BACKGROUND

Preclinical low-count positron emission tomography (LC-PET) imaging offers numerous advantages such as facilitating imaging logistics, enabling longitudinal studies of long- and short-lived isotopes as well as increasing scanner throughput. However, LC-PET is characterized by reduced photon-count levels resulting in low signal-to-noise ratio (SNR), segmentation difficulties, and quantification uncertainties.

PURPOSE

We developed and evaluated a novel deep-learning (DL) architecture-Attention based Residual-Dilated Net (ARD-Net)-to generate standard-count PET (SC-PET) images from LC-PET images. The performance of the ARD-Net framework was evaluated for numerous low count realizations using fidelity-based qualitative metrics, task-based segmentation, and quantitative metrics.

METHOD

Patient Derived tumor Xenograft (PDX) with tumors implanted in the mammary fat-pad were subjected to preclinical [18F]-Fluorodeoxyglucose (FDG)-PET/CT imaging. SC-PET images were derived from a 10 min static FDG-PET acquisition, 50 min post administration of FDG, and were resampled to generate four distinct LC-PET realizations corresponding to 10%, 5%, 1.6%, and 0.8% of SC-PET count-level. ARD-Net was trained and optimized using 48 preclinical FDG-PET datasets, while 16 datasets were utilized to assess performance. Further, the performance of ARD-Net was benchmarked against two leading DL-based methods (Residual UNet, RU-Net; and Dilated Network, D-Net) and non-DL methods (Non-Local Means, NLM; and Block Matching 3D Filtering, BM3D). The performance of the framework was evaluated using traditional fidelity-based image quality metrics such as Structural Similarity Index Metric (SSIM) and Normalized Root Mean Square Error (NRMSE), as well as human observer-based tumor segmentation performance (Dice Score and volume bias) and quantitative analysis of Standardized Uptake Value (SUV) measurements. Additionally, radiomics-derived features were utilized as a measure of quality assurance (QA) in comparison to true SC-PET. Finally, a performance ensemble score (EPS) was developed by integrating fidelity-based and task-based metrics. Concordance Correlation Coefficient (CCC) was utilized to determine concordance between measures. The non-parametric Friedman Test with Bonferroni correction was used to compare the performance of ARD-Net against benchmarked methods with significance at adjusted p-value ≤0.01.

RESULTS

ARD-Net-generated SC-PET images exhibited significantly better (p ≤ 0.01 post Bonferroni correction) overall image fidelity scores in terms of SSIM and NRMSE at majority of photon-count levels compared to benchmarked DL and non-DL methods. In terms of task-based quantitative accuracy evaluated by SUVMean and SUVPeak, ARD-Net exhibited less than 5% median absolute bias for SUVMean compared to true SC-PET and lower degree of variability compared to benchmarked DL and non-DL based methods in generating SC-PET. Additionally, ARD-Net-generated SC-PET images displayed higher degree of concordance to SC-PET images in terms of radiomics features compared to non-DL and other DL approaches. Finally, the ensemble score suggested that ARD-Net exhibited significantly superior performance compared to benchmarked algorithms (p ≤ 0.01 post Bonferroni correction).

CONCLUSION

ARD-Net provides a robust framework to generate SC-PET from LC-PET images. ARD-Net generated SC-PET images exhibited superior performance compared other DL and non-DL approaches in terms of image-fidelity based metrics, task-based segmentation metrics, and minimal bias in terms of task-based quantification performance for preclinical PET imaging.

Utility of MRI in detection of PET-CT proven local recurrence of pancreatic adenocarcinoma after surgery

The aim of this prospective study was to investigate the accuracy and inter-observer reliability of MRI in detection of local recurrence (LR) of pancreatic adenocarcinoma (PAC) after surgery, which was proved by PET-CT and access correlation between functional MRI and PET parameters. Forty-five patients who underwent PET-CT and MRI for follow-up purposes after radical operation of PAC were included. Twenty-three were PET positive (study group) and 22 negative for LR (control group). MR examination was performed within one month after PET-CT and three readers who were blind for PET-CT findings searched LR in T2W, 3D-dynamic post-contrast T1W-FS and DWI sequences, respectively. Sensitivity and specificity were calculated while inter-reader agreement was estimated by Cronbach's Alpha reliability coefficient (CARC). Apparent diffusion coefficient (ADC) of LR was correlated with the size (maximal diameter) and functional PET-CT parameters: mean and maximum standardized uptake values (SUVmean, SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG), using Spearman's correlation coefficient (rS). Sensitivity and specificity among three readers in detecting the LR were 70% and 77-84% in T2W (CARC 0.806), 91-100% and 100% in 3D post-contrast T1W-FS (CARC 0.980), and both 100% in DWI sequences (CARC 1.000). Moderate inverse correlation was found between the ADC and SUVmean (rS = - 0.484), MTV (rS = - 0.494), TLG (rS = - 0.519) and lesion size (rS = - 0.567). MRI with DWI shows high diagnostic accuracy in detecting the LR of PAC in comparison to PET-CT as reference standard. ADC significantly inversely correlates with standard and advanced PET parameters and size of LR.

A computational approach for analysis of intratumoral heterogeneity and standardized uptake value in PET/CT images1

BACKGROUND

By providing both functional and anatomical information from a single scan, digital imaging technologies like PET/CT and PET/MRI hybrids are gaining popularity in medical imaging industry. In clinical practice, the median value (SUVmed) receives less attention owing to disagreements surrounding what defines a lesion, but the SUVmax value, which is a semi-quantitative statistic used to analyse PET and PET/CT images, is commonly used to evaluate lesions.

OBJECTIVE

This study aims to build an image processing technique with the purpose of automatically detecting and isolating lesions in PET/CT images, as well as measuring and assessing the SUVmed.

METHODS

The pictures are separated into their respective lesions using mathematical morphology and the crescent region, which are both part of the image processing method. In this research, a total of 18 different pictures of lesions were evaluated.

RESULTS

The findings of the study reveal that the threshold is satisfied by both the SUVmax and the SUVmed for most of the lesion types. However, in six instances, the SUVmax and SUVmed values are found to be in different courts.

CONCLUSION

The new information revealed by this study needs to be further investigated to determine if it has any practical value in diagnosing and monitoring lesions. However, results of this study suggest that SUVmed should receive more attention in the evaluation of lesions in PET and CT images.

Relationship between the expression of PD-L1 and 18F-FDG uptake in pancreatic ductal adenocarcinoma

BACKGROUND

PD-L1 promotes glycolysis in tumour cells. We observed a correlation between high PD-L1 expression and high 18F-FDG uptake in patients with pancreatic ductal adenocarcinoma (PDAC) in a previous study. This study aims to determine the usefulness of 18F-FDG PET/CT for evaluating the PD-L1 status in PDAC and to elucidate its rationality by integrated analyses.

METHODS

For bioinformatics analysis, WGCNA, GSEA and TIMER were applied to analyse the pathways and hub genes associated with PD-L1 and glucose uptake. 18F-FDG uptake assay was used to determine the glucose uptake rate of PDAC cells in vitro. Related genes expression were verified by RT-PCR and western blot. A retrospective analysis was performed on 47 patients with PDAC who had undergone 18F-FDG PET/CT. Maximum standardised uptake values (SUVmax) were determined. The usefulness of SUVmax for evaluating PD-L1 status was determined by receiver operating characteristic (ROC) curve analysis.

RESULTS

Bioinformatics analysis showed that several signalling pathways are associated with both PD-L1 expression and tumour glucose uptake, among which JAK-STAT may be an important one. By in vitro experiments, the regulatory role of PD-L1 on glucose uptake was demonstrated, and its dependency on the JAK-STAT pathway was also verified by the rescue study. The SUVmax of PD-L1-positive patients was significantly higher than PD-L1-negative in tumour cells (TCs) (6.1 ± 2.3 vs. 11.1 ± 4.2; P < 0.001), and in tumour-infiltrating immune cells (TIICs) (6.4 ± 3.2 vs. 8.4 ± 3.5; P < 0.001). In a multivariate analysis, SUVmax was significantly associated with PD-L1 expression in TCs and TIICs (P < 0.001 and P = 0.018, respectively). Using SUVmax cut-off values of 8.15 and 7.75, PD-L1 status in TCs and TIICs could be predicted with accuracies of 91.5% and 74.5%, respectively.

CONCLUSION

Higher 18F-FDG uptake by PDAC is associated with elevated PD-L1 expression. JAK-STAT is an important pathway that mediates PD-L1 to promote glucose uptake in PDAC.

Metabolic kinetic modeling of [11C]methionine based on total-body PET in multiple myeloma

PURPOSE

Multiple myeloma (MM) is a malignant disease characterized by the secretion of monoclonal immunoglobulins and has a high demand for amino acids. [11C]methionine total-body PET is capable of noninvasive dynamic monitoring of radiotracer in vivo, thus providing a way to reveal the dynamic changes of myeloma metabolism. This study aims to analyze the metabolic process of [11C]methionine based on kinetic modeling, and to preliminary reveal its application value in MM.

METHODS

Dynamic total-body [11C]methionine PET/CT was conducted with uEXPLORER in 12 subjects (9 MM patients and 3 controls). The tissue time activity curves (TACs) of organs and bone marrows were extracted. Model fitting of TACs was operated using PMOD Kinetic Modeling. After validation by Goodness of fit (GOF), the reversible two-tissue compartment model (2T4k) was used to further analysis. R software was used to analyze the correlation between kinetic parameters and clinical indicators.

RESULTS

The 2T4k has passed the criterion of GOF and was used to fit the data of 0-20 minutes. The [11C]methionine net uptake rate (Ki) was significantly higher in the MM lesions than in the non-myeloma controls (control: 0.040±0.007 mL/g/min, MM: 0.171±0.108 mL/g/min, p=0.009). The Ki values were found to be correlated with M protein levels in MM patients. MM patients with t(4;14) translocations had an elevated k4 value compared with t(4;14) negative patients.

CONCLUSION

MM lesions have a propensity for uptake of [11C]methionine. The serum levels of M protein are correlated with [11C]methionine uptake rate in myeloma. Metabolic classification based on the k4 value may be a promising strategy for risk stratification in MM.

Evaluation of cellular water exchange in a mouse glioma model using dynamic contrast-enhanced MRI with two flip angles

This manuscript aims to evaluate the robustness and significance of the water efflux rate constant (k_io) parameter estimated using the two flip-angle Dynamic Contrast-Enhanced (DCE) MRI approach with a murine glioblastoma model at 7 T. The repeatability of contrast kinetic parameters and k_io measurement was assessed by a test-retest experiment (n = 7). The association of k_io with cellular metabolism was investigated through DCE-MRI and FDG-PET experiments (n = 7). Tumor response to a combination therapy of bevacizumab and fluorouracil (5FU) monitored by contrast kinetic parameters and k_io (n = 10). Test-retest experiments demonstrated compartmental volume fractions (v_e and v_p) remained consistent between scans while the vascular functional measures (F_p and PS) and k_io showed noticeable changes, most likely due to physiological changes of the tumor. The standardized uptake value (SUV) of tumors has a linear correlation with k_io (R² = 0.547), a positive correlation with F_p (R² = 0.504), and weak correlations with v_e (R² = 0.150), v_p (R² = 0.077), PS (R² = 0.117), K^trans (R² = 0.088) and whole tumor volume (R² = 0.174). In the treatment study, the k_io of the treated group was significantly lower than the control group one day after bevacizumab treatment and decreased significantly after 5FU treatment compared to the baseline. This study results support the feasibility of measuring k_io using the two flip-angle DCE-MRI approach in cancer imaging.

Evaluation of standardized uptake value on 131I-6β-iodomethyl-19-norcholesterol scintigraphy for diagnosis of primary aldosteronism and correspondence with adrenal venous sampling

PURPOSE

Adrenal venous sampling (AVS) is a reliable method for lateralization of adrenal hormone secretion, which is important for discriminating between aldosterone-producing adenoma and bilateral adrenal hyperplasia, both of which cause primary aldosteronism (PA). The aim of this study was to evaluate the diagnostic accuracy of the maximum and mean standardized uptake values (SUV_max and SUV_mean, respectively) of ¹³¹I-6β-iodomethyl-19-norcholesterol (NP-59) single-photon emission computed tomography (SPECT) for PA and its correspondence with AVS.

METHODS

Adrenal NP-59 scintigraphy was performed in 14 patients with suspected PA, and AVS was also performed in 7 of them. SUV_max and SUV_mean of the adrenal lesions on the dominant side and their ratios to the values on the non-dominant side (SUVR_max and SUVR_mean, respectively) were calculated on SPECT images using ordered-subset conjugate gradient minimization (OSCGM) and three-dimensional ordered-subset expectation maximization (3D-OSEM) reconstruction algorithms.

RESULTS

SUV_max and SUV_mean on NP-59 SPECT images were significantly higher for aldosterone-producing adenoma than for bilateral adrenal hyperplasia or non-functioning adenoma and slightly superior to SUVR_max and SUVR_mean (P = 0.0475 and P = 0.0447 vs. P = 0.124 and P = 0.132, respectively, with OSCGM). The respective areas under the receiver-operating characteristic curve for SUV and SUVR were 0.933 and 0.725 with OSCGM and 0.844 and 0.750 with 3D-OSEM, while SUV_max and SUVR_max had exactly the same diagnostic accuracy as SUV_mean and SUVR_mean. SUV and SUVR were associated with the diagnostic features on AVS and consistent with lateralization by AVS in most patients.

CONCLUSION

In this study, SUV on NP-59 SPECT helped in the diagnosis of PA and was consistent with the results of AVS in nearly all cases.

18F-FDG PET/CT scan standardised uptake value (SUV) score for diagnosis, staging and monitoring malignancy in spinal melanotic schwannoma

Melanotic schwannoma (MS) is a rare nerve sheath neuroectodermal neoplasm. We highlight the use of F18-fluorodeoxyglucose positive emission tomography/computed tomography (18F-FDG PET/CT) standardised uptake value (SUV) results in the diagnosis, staging and monitoring of spinal MS. A 58-year-old female patient had a 6-month history of left leg pain (S1) and no skin lesions. Magnetic resonance imaging reported a possible schwannoma with CT-guided biopsy, indicating a metastatic malignant melanoma. 18F-FDG PET/CT scan revealed only sacral destruction and an SUV score of 3.6. Histopathology results confirmed a malignant melanotic peripheral nerve sheath tumour (schwannoma). In MS, the 18F-FDG PET/CT scan SUV cut-off point can be used to distinguish between benign and malignant lesions, whereas (SUVmax) can predict the histologic response and therefore useful as a ‘screening test’. Our case highlights the increased uptake on PET/CT by melanocytic variant of neurogenic tumours and clinicians need to be aware of this.

EFFECTIVE DOSE ESTIMATION IN WHOLE BODY 18F-FDG PET/CT IMAGING

Positron emission tomography-computed tomography (PET-CT) with internal administration of the FDG-18 is characterized as a widespread functional imaging modality in diagnostic radiation medicine, which increases the patient effective doses owing to the presence of internal and external radiation sources. Hence, patient effective dose estimation has been pinpointed as a significant factor in radiation protection assessment. A large number of studies have been published in this regard, and various dosimetry methods have been surveyed. According to our previous research, 10 patients had participated in PET-CT scans with three static time sequences imaging. PET effective doses were estimated using a simple method derived from Anderson et al. and Kaushik et al. coefficients, and the CT effective doses were surveyed with a CTDI phantom and cylindrical ionization chamber. The CT dose was tripled owing to the three static time-sequences imaging. The effective doses were calculated using different coefficients and the results of the PET effective doses were compared. The PET-CT effective dose was varied from 17.14 to 18.42 mSv based on Kaushik et al. coefficients which were measured for one low-dose CT scan. This study aimed to survey simple PET-CT effective dose estimation using three static-time imaging approaches which increases the total patient effective doses.

Prognostic Significance of FDG PET/CT in Esophageal Squamous Cell Carcinoma in the Era of the 8th AJCC/UICC Staging System

Introduction

Recently, the American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) staging system was updated for its 8th edition. F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) is a useful imaging tool to diagnose and predict prognoses for esophageal cancer. However, there was no previous study to explore the role of FDG PET/CT in the staging system based on the 8th edition. The prognostic value of FDG PET/CT was investigated in patients with esophageal squamous cell carcinoma (SqCC) considering the new 8th AJCC/UICC staging system.

Methods

Subjects were 721 patients with esophageal SqCC undergoing pretherapeutic FDG PET/CT. Clinico-pathological variables and the maximum standardized uptake value (SUVmax) of the primary tumor were included in survival analysis. Subgroup analysis was performed to compare hazard ratios according to pathological stage and SUVmax. A new staging classification including FDG uptake was proposed.

Results

In multivariate survival analysis, pathological stage and SUVmax of the primary tumor were selected as independent prognostic factors for overall survival in both the 7th and 8th editions. The proposed new staging system showed better discrimination for overall survival between stage I and II than did the conventional staging system (hazard ratios: 2.250 vs. 1.341).

Conclusions

The FDG uptake of the primary tumor was found to be an independent prognostic factor along with pathological stage based on both 7th and 8th AJCC/UICC staging systems in patients with esophageal SqCC. The suggested new staging system including SUVmax was better for predicting prognoses than the conventional staging system.

Clinical Perspectives for 18F-FDG PET Imaging in Pediatric Oncology: Μetabolic Tumor Volume and Radiomics

Pediatric cancer, although rare, requires the most optimized treatment approach to obtain high survival rates and minimize serious long-term side effects in early adulthood. 18F-FDG PET/CT is most helpful and widely used in staging, recurrence detection, and response assessment in pediatric oncology. The well-known 18F-FDG PET metabolic indices of metabolic tumor volume (MTV) and tumor lesion glycolysis (TLG) have already revealed an independent significant prognostic value for survival in oncologic patients, although the corresponding cut-off values remain study-dependent and not validated for use in clinical practice. Advanced tumor “radiomic” analysis sheds new light into these indices. Numerous patterns of texture 18F-FDG uptake features can be extracted from segmented PET tumor images due to new powerful computational systems supporting complex “deep learning” algorithms. This high number of “quantitative” tumor imaging data, although not decrypted in their majority and once standardized for the different imaging systems and segmentation methods, could be used for the development of new “clinical” models for specific cancer types and, more interestingly, for specific age groups. In addition, data from novel techniques of tumor genome analysis could reveal new genes as biomarkers for prognosis and/or targeted therapies in childhood malignancies. Therefore, this ever-growing information of “radiogenomics”, in which the underlying tumor “genetic profile” could be expressed in the tumor-imaging signature of “radiomics”, possibly represents the next model for precision medicine in pediatric cancer management. This paper reviews 18F-FDG PET image segmentation methods as applied to pediatric sarcomas and lymphomas and summarizes reported findings on the values of metabolic and radiomic features in the assessment of these pediatric tumors.

Prognostic Significance of FDG PET/CT in Esophageal Squamous Cell Carcinoma in the Era of the 8th AJCC/UICC Staging System

INTRODUCTION

Recently, the American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) staging system was updated for its 8th edition. F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) is a useful imaging tool to diagnose and predict prognoses for esophageal cancer. However, there was no previous study to explore the role of FDG PET/CT in the staging system based on the 8th edition. The prognostic value of FDG PET/CT was investigated in patients with esophageal squamous cell carcinoma (SqCC) considering the new 8th AJCC/UICC staging system.

METHODS

Subjects were 721 patients with esophageal SqCC undergoing pretherapeutic FDG PET/CT. Clinico-pathological variables and the maximum standardized uptake value (SUVmax) of the primary tumor were included in survival analysis. Subgroup analysis was performed to compare hazard ratios according to pathological stage and SUVmax. A new staging classification including FDG uptake was proposed.

RESULTS

In multivariate survival analysis, pathological stage and SUVmax of the primary tumor were selected as independent prognostic factors for overall survival in both the 7th and 8th editions. The proposed new staging system showed better discrimination for overall survival between stage I and II than did the conventional staging system (hazard ratios: 2.250 vs. 1.341).

CONCLUSIONS

The FDG uptake of the primary tumor was found to be an independent prognostic factor along with pathological stage based on both 7th and 8th AJCC/UICC staging systems in patients with esophageal SqCC. The suggested new staging system including SUVmax was better for predicting prognoses than the conventional staging system.

Toward Reliable Uptake Metrics in Large Vessel Vasculitis Studies

The aim of this study is to investigate the influence of sex, age, fat mass, fasting blood glucose level (FBGL), and estimated glomerular filtration rate (eGFR) on blood pool activity in patients with large vessel vasculitis (LVV). Blood pool activity was measured in the superior caval vein using mean, maximum, and peak standardized uptake values corrected for body weight (SUVs) and lean body mass (SULs) in 41 fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scans of LVV patients. Sex influence on the blood pool activity was assessed with t-tests, while linear correlation analyses were used for age, fat mass, FBGL, and eGFR. Significantly higher SUVs were found in women compared with men, whereas SULs were similar between sexes. In addition, higher fat mass was associated with increased SUVs (r = 0.56 to 0.65; all p < 0.001) in the blood pool, but no correlations were found between SULs and fat mass (r = −0.25 to −0.15; all p > 0.05). Lower eGFR was associated with a higher FDG blood pool activity for all uptake values. In FDG-PET/CT studies with LVV patients, we recommend using SUL over SUV, while caution is advised in interpreting SUV and SUL measures when patients have impaired kidney function.

Pretreatment maximum standardized uptake value in 18F-fluorodeoxyglucose positron emission tomography-computed tomography as a prognostic factor for ovarian clear cell carcinoma and low-grade serous carcinoma

OBJECTIVE

The maximum standardized uptake value (SUVmax) derived by positron emission tomography-computed tomography (PET/CT) can be an index of biological tumor aggressiveness, which is assessed using noninvasive tools before the treatment of epithelial ovarian cancer (EOC). This study aimed to evaluate the prognostic value of the pretreatment SUVmax in patients with EOC.

MATERIALS AND METHODS

We reviewed the data of patients with EOC who underwent pretreatment 18F-FDG PET/CT between June 2006 and September 2016. The relationships between pretreatment SUVmax and histological subtypes of EOC were determined. Moreover, progression-free survival (PFS) and overall survival (OS) were evaluated according to the pretreatment SUVmax. Risk factors associated with progression or death were also analyzed.

RESULTS

Of 148 patients, 66 (44.6%), 11 (7.4%), 34 (23.0%), 19 (12.8%), 15 (10.1%), and three (2.0%) were diagnosed with high-grade serous carcinoma (HGSC), low-grade serous carcinoma (LGSC), clear cell carcinoma (CCC), endometrioid carcinoma, mucinous carcinoma, and others, respectively. The median SUVmax was marginally lower in LGSC (6.80 vs. 10.5; P = 0.059) and significantly lower in CCC (5.92 vs. 10.5; P = 0.001) than in HGSC. A high pretreatment SUVmax (≥9.30) was a prognostic factor for OS in patients with LGSC (P = 0.046). Furthermore, multivariate analysis revealed that a high SUVmax (≥5.85) was an independent prognostic factor for OS (P = 0.046) in patients with CCC. However, a high SUVmax (≥7.77) was a poor predictor of PFS and OS in patients with EOC (P = 0.156 and P = 0.158, respectively).

CONCLUSION

Our findings suggest that the pretreatment SUVmax is not only an independent predictor of survival in patients with CCC but also a significant predictor of survival in patients with LGSC.

Correlation of texture feature analysis with bone marrow infiltration in initial staging of patients with lymphoma using 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography

Purpose

To explore whether radiomic features of fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomo-graphy-computed tomography (PET/CT) has association with bone marrow infiltration (BMI) in comparison to other conventional PET metrics.

Material and methods

Forty-four patients (with pathologically proven lymphoma disease) underwent staging ¹⁸F-FDG PET/CT scan. Primary tumour was semi-automatically or manually segmented with a threshold standardised uptake value (SUV) of 3. A total of 73 features were extracted from eight different textures. Spearman correlation was used to test the correlation of features with conventional quantitative metrics such as SUV, metabolic tumour volume, and total lesion glycolysis. Specificity and sensitivity (including 95% confidence intervals [CI]) for each of the studied parameters were derived using receiver operative characteristic (ROC) curves. Univariate and multivariate analyses were used to identify independent predictors associated with BMI.

Results

Correlation between conventional PET metrics and features ranged between 0.50 and 0.97 for positive correlation (33 significant association features) and ranged from -0.52 to -0.97 for inverse correlation (three significant association features) for both strong and moderate correlations. Analysis of ROC curves showed that high-intensity long-run emphasis 4 bin, high-intensity large zone emphasis 64 bin, long-run emphasis (LRE) 64 bin, large-zone emphasis 64 bin, max spectrum 8 bin, busyness 64 bin, and code similarity 32 and 64 bin were significant discriminators of BMI among other features (area under curve > 0.682, p < 0.05). Univariate analyses of texture features showed that code similarity and long-run emphasis (both 64 bin) were significant predictors of bone marrow involvement. Multivariate analyses revealed that LRE (64 bin, p = 0.031) with an odds ratio of 1.022 and 95% CI of (1.002-1.043) were independent variables for bone marrow involvement.

Conclusions

¹⁸F-FDG PET/CT radiomic features are synergistic to visual assessment of BMI in patients diagnosed with lymphoma using ¹⁸F-FDG PET/CT. Further assessment of long-run emphasis is highly warranted.

Pyruvate-lactate exchange and glucose uptake in human prostate cancer cell models. A study in xenografts and suspensions by hyperpolarized [1-13 C]pyruvate MRS and [18 F]FDG-PET

Reprogramming of energy metabolism in the development of prostate cancer can be exploited for a better diagnosis and treatment of the disease. The goal of this study was to determine whether differences in glucose and pyruvate metabolism of human prostate cancer cells with dissimilar aggressivenesses can be detected using hyperpolarized [1-¹³ C]pyruvate MRS and [¹⁸ F]FDG-PET imaging, and to evaluate whether these measures correlate. For this purpose, we compared murine xenografts of human prostate cancer LNCaP cells with those of more aggressive PC3 cells. [1-¹³ C]pyruvate was hyperpolarized by dissolution dynamic nuclear polarization (dDNP) and [1-¹³ C]pyruvate to lactate conversion was followed by ¹³ C MRS. Subsequently [¹⁸ F]FDG uptake was investigated by static and dynamic PET measurements. Standard uptake values (SUVs) for [¹⁸ F]FDG were significantly higher for xenografts of PC3 compared with those of LNCaP. However, we did not observe a difference in the average apparent rate constant k_pl of ¹³ C label exchange from pyruvate to lactate between the tumor variants. A significant negative correlation was found between SUVs from [¹⁸ F]FDG PET measurements and k_pl values for the xenografts of both tumor types. The k_pl rate constant may be influenced by various factors, and studies with a range of prostate cancer cells in suspension suggest that LDH inhibition by pyruvate may be one of these. Our results indicate that glucose and pyruvate metabolism in the prostate cancer cell models differs from that in other tumor models and that [¹⁸ F]FDG-PET can serve as a valuable complementary tool in dDNP studies of aggressive prostate cancer with [1-¹³ C]pyruvate.

Quantification of [18F]UCB-H Binding in the Rat Brain: From Kinetic Modelling to Standardised Uptake Value

PURPOSE

[¹⁸F]UCB-H is a specific positron emission tomography (PET) biomarker for the Synaptic Vesicle protein 2A (SV2A), the binding site of the antiepileptic drug levetiracetam. With a view to optimising acquisition time and simplifying data analysis with this radiotracer, we compared two parameters: the distribution volume (Vt) obtained from Logan graphical analysis using a Population-Based Input Function, and the Standardised Uptake Value (SUV).

PROCEDURES

Twelve Sprague Dawley male rats, pre-treated with three different doses of levetiracetam were employed to develop the methodology. Three additional kainic acid (KA) treated rats (temporal lobe epilepsy model) were also used to test the procedure. Image analyses focused on: (i) length of the dynamic acquisition (90 versus 60 min); (ii) correlations between Vt and SUV over 20-min consecutive time-frames; (iii) and (iv) evaluation of differences between groups using the Vt and the SUV; and (v) preliminary evaluation of the methodology in the KA epilepsy model.

RESULTS

A large correlation between the Vt issued from 60 to 90-min acquisitions was observed. Further analyses highlighted a large correlation (r > 0.8) between the Vt and the SUV. Equivalent differences between groups were detected for both parameters, especially in the 20-40 and 40-60-min time-frames. The same results were also obtained with the epilepsy model.

CONCLUSIONS

Our results enable the acquisition setting to be changed from a 90-min dynamic to a 20-min static PET acquisition. According to a better image quality, the 20-40-min time-frame appears optimal. Due to its equivalence to the Vt, the SUV parameter can be considered in order to quantify [¹⁸F]UCB-H uptake in the rat brain. This work, therefore, establishes a starting point for the simplification of SV2A in vivo quantification with [¹⁸F]UCB-H, and represents a step forward to the clinical application of this PET radiotracer.

Optimising the selection of candidates for neoadjuvant chemotherapy amongst patients with node-positive penile squamous cell carcinoma

OBJECTIVES

To identify predictors of poor overall survival (OS) amongst patients with penile squamous cell carcinoma (pSCC) with clinical inguinal lymphadenopathy (cN+), in order to define the best candidates for neoadjuvant chemotherapy (NAC).

PATIENTS AND METHODS

Using an international, multicentre database of 924 patients with pSCC, we identified 334 men who harboured cN+ with available clinical and follow-up data. Lymph node involvement was defined either by the presence of palpable inguinal node disease or by preoperative computed tomography (CT) assessment. Fluorine-18 fluorodeoxyglucose positron-emission tomography (¹⁸ F-FDG-PET)/CT scan was performed based on clinical judgment of the treating physician. Regression-tree analysis generated a risk stratification tool for prediction of 24-month overall mortality (OM). Kaplan-Meier explored the OS benefit related to the use of NAC according to the regression-tree-stratified subgroups.

RESULTS

Overall, 120 (35.9%), 152 (45.5%), and 62 (18.6%) patients harboured cN1, cN2, and cN3 disease. ¹⁸ F-FDG-PET/CT was performed in 48 (14.4%) patients, and 16 (4.8%) had inguinal and pelvic nodal PET detection. The median OS was 107 months, with a 24-month OS of 66%. At regression-tree analysis (area under the curve = 70%), patients with cN3 and cN2 with PET/CT-detected inguinal and pelvic nodal activity had a higher risk of 24-month OM (>50%). NAC was associated with improved 24-month OS rates (54% vs 33%) only in this subgroup of patients (P = 0.002), which was also confirmed after multivariable adjustment (hazard ratio 0.28, 95% confidence interval 0.13-0.62; P = 0.002).

CONCLUSION

Patients with pSCC with cN3 or cN2 and inguinal and pelvic 18F-FDG-PET/CT scan detected disease had higher 24-month OM rates according to our regression-tree model. NAC was associated with improved OS only in these subgroups of patients. Our novel decision model may help to stratify cN+ patients, and identify those who most likely will benefit from NAC prior to radical surgical resection.

[Verification of Image Reconstruction Method and Collimator Suitable for Quantitative Analysis of Striatum in Dopamine Transporter Scintigraphy]

Specific binding ratio (SBR) is mainly used as a quantitative index of dopamine transporter scintigraphy, although it was reported that standardized uptake value (SUV) is useful for clinical diagnosis in recent years. The aim of this study is to evaluate whether xSPECT is useful for SUV in dopamine transporter scintigraphy. xSPECT is a recently developed, high-resolution image reconstruction technique that transforms single photon emission computed tomography (SPECT) to a computed tomography (CT) coordinate system. Furthermore, low-penetration high-resolution (LPHR), which there has been no previous physical evaluation report was also evaluated. The radioactive concentration of the image with xSPECT is automatically calculated by the periodic sensitivity calibration and one volume sensitivity calibration. In the case of images with conventional reconstruction methods as filtered back projection (FBP) and ordered subset expectation maximization (OSEM), the calibration factor related to the photon count and radioactive concentration was calculated from measuring a cylinder phantom filled with Iodine-123. Radioactive concentrations of the SUV factor were measured by SPECT data acquisition with the striatal phantom in various conditions. Radioactive concentrations with conventional reconstruction methods had a lower value (for example, with FBP it was 7.53 kBq/ml, with OSEM it was 7.22 kBq/ml) compared to the actual measurement value, although that with xSPECT (12.45 kBq/ml) got close to the actual measurement value (14.68 kBq/ml). LPHR showed an approximation to low-energy high-resolution (LEHR) in terms of spatial resolution and scatter fraction estimated from energy windows. The quantitative accuracy of radioactive concentration was the highest under xSPECT.

Assessing PET Parameters in Oncologic 18F-FDG Studies

PET imaging, particularly oncologic applications of ¹⁸F-FDG, has become a routine diagnostic study. To better describe malignancies, various PET parameters are used. In ¹⁸F-FDG PET studies, SUV_max is the most commonly used parameter to measure the metabolic activity of the tumor. In obese patients, SUV corrected by lean body mass (SUL), and in pediatric patients, SUV corrected by body surface area, are recommended. Metabolic tumor volume is an important parameter to determine the local and total tumor burden. Total lesion glycolysis (SUV_mean × metabolic tumor volume) provides information about averages. Some treatment response assessment protocols recommend using the SUV_peak or SUL_peak of the tumor. Tumor-to-liver ratio and tumor-to-blood-pool ratio are helpful when comparing studies for treatment response assessment. Dual-time-point PET imaging with retention index can help differentiate malignant from benign lesions and may help detect small lesions. Dynamic ¹⁸F-FDG PET imaging and quantitative analysis can measure the metabolic, phosphorylation, and dephosphorylation rates of lesions but are mainly used for research purposes. In this article, we will review the currently available PET parameters in ¹⁸F-FDG studies with their importance, uses, limitations, and reasons for erroneous results.

Quantitative imaging biomarkers in nuclear medicine: from SUV to image mining studies. Highlights from annals of nuclear medicine 2018

OBJECTIVE

Quantification in medical imaging is one of the main goals in research and clinical practice since it allows immediate understanding, objective communication, and comparison. Our aim was to summarize relevant investigations on quantification in nuclear medicine studies published in the volume 32 of Annals of Nuclear Medicine.

METHODS

In this article, we summarized the data of 14 selected papers from international research groups that were published between January and December 2018. This is a descriptive review with an inherently subjective selection of articles.

RESULTS

We discussed the role of parameters ranging from standardized uptake value to ratios, to flow within a region of interest, to volumetric parameters and to texture indices in different clinical scenarios in oncology, cardiology, and neurology.

CONCLUSIONS

In all the medical disciplines in which nuclear medicine examinations play a role, quantification is essential both in research and in clinical practice. Standardization and high-quality protocols are crucial for the success and reliability of imaging biomarkers.

Revisiting Weight-Normalized SUV and Lean-Body-Mass-Normalized SUV in PET Studies

SUV normalized by total body weight is affected by the amount of body fat. The SUV of normal tissues and lesions is higher (overestimated) in obese patients than in patients with a normal body mass index (BMI). SUL (SUV normalized by lean body mass [LBM]) is recommended for more accurate SUV results. Given the importance of a quantitative PET parameter, particularly when comparing PET studies, we aimed to revisit the effect of obesity on SUV, measuring SUL in normal-BMI patients and obese patients and testing the effect of the amount of LBM. Methods: ¹⁸F-FDG whole-body images of adult patients were analyzed retrospectively. We measured both SUV_max and SUV_mean in the blood pool and liver of patients with a normal BMI (18.5-24.9) and a high BMI (≥30) (obese). In all patients, we calculated LBM via an equation using patient height and weight and corrected all SUVs to SULs. Mean (±SD) SUVs and SULs were compared under various circumstances. Scatterplots were generated for weight and SUV-SUL differences. Results: SUV_mean in the liver and blood pool was significantly higher in obese patients (30 patients) than in patients with a normal BMI (20 patients) (4.1 ± 0.7 and 3.0 ± 0.5, respectively, in liver, vs. 3.2 ± 0.6 and 2.4 ± 0.4, respectively, in blood pool; P < 0.001). SUL_mean was significantly lower in both liver and blood pool in all patients, being approximately 75% of SUV_mean in patients with a normal BMI and 55% of SUV_mean in obese patients (P < 0.001). SUL_mean in the liver and blood pool did not significantly differ between obese patients and normal-BMI patients (P > 0.05). The SUV-SUL difference was significantly higher in obese patients than in patients with a normal BMI (P < 0.001). These statistical results were the same when SUV_max and SUL_max were compared. Conclusion: SUV overestimates metabolic activity in all patients, and this overestimation is more significant in obese patients than in patients with a normal BMI. SUL is not affected by body weight or the amount of LBM.

Evaluation of cell viability and metabolic activity of a 3D cultured human epidermal model using a dynamic autoradiographic technique with a PET radiopharmaceutical

Quality control of tissues and organs for transplant is important to confirm their safety and effectiveness for regenerative medicine. However, quality evaluation is only carried out using a limited range of inspection criteria, because many of the available evaluation tests are invasive. In order to explore the potential of 2-[¹⁸F]fluoro-2-deoxy-D-glucose ([¹⁸F]FDG)-bioradiography as a non-invasive test for estimation of the safety, soundness, and effectiveness of tissues for transplantation, [¹⁸F]FDG uptake and cell viability or metabolism were investigated using a reconstructed human epidermal model (RHEM). We developed an imaging system, and suitable bioradiographic image acquisition conditions and its effectiveness were investigated. [¹⁸F]FDG uptake increased in agreement with DNA content as a marker of cell numbers and for histological assessment during cell proliferation and keratinization. [¹⁸F]FDG uptake was significantly decreased in good agreement with the viability of tissues used with various hazardous chemical treatments. [¹⁸F]FDG uptake by the tissues was decreased by hypothermia treatment and increased by hypoxia treatment while maintaining cell viability in the tissue. Therefore, [¹⁸F]FDG-bioradiography can be useful to estimate cell viability or metabolism in this RHEM. This method might be utilized as a non-invasive test for quality evaluation of tissues for transplantation.

Symmetry and spatial distribution of muscle glucose uptake in the lower limbs during walking measured using FDG-PET

Purpose

This study aimed to elucidate whether muscle activity (in terms of glucose uptake) between the legs can be considered symmetrical during walking. Furthermore, we aimed to determine whether the [¹⁸F]-fluorodeoxyglucose was distributed heterogeneously throughout each muscle, and if so, whether areas of high uptake would be clustered.

Methods

Ten healthy participants walked on a treadmill at self-selected comfortable walking speed for a total of 90 minutes, 60 minutes before and 30 minutes after intravenous injection of 50 MBq [¹⁸F]-fluorodeoxyglucose. Thereafter, a positron emission tomography/computed tomography scan of the lower limb was acquired. Three-dimensional muscle contours of 78 (= 39x2) muscles of the left and right lower limb were semi-automatically determined from magnetic resonance imaging scans. After non-rigid registration, those muscle contours were used to extract [¹⁸F]-fluorodeoxyglucose uptake from the positron emission tomography scans.

Results

Large asymmetries were observed in the lower leg muscles (e.g. median absolute asymmetry index of 42% in the gastrocnemius medialis) and in the gluteus minimus (30% asymmetry) and gluteus medius (15% asymmetry), whereas the uptake in the thighs was relatively symmetrical between the limbs (<6% asymmetry). These were not related to limb-dominance nor to inter-limb differences in muscle volume. The [¹⁸F]-fluorodeoxyglucose distribution was not distributed normally; most voxels had a relatively low standardized uptake value, and a minority of voxels had a relatively high standardized uptake value. The voxels with higher [¹⁸F]-fluorodeoxyglucose uptake were distributed heterogeneously; they were clustered in virtually all muscles.

Conclusion

The findings in this study challenge the common assumption of symmetry in muscle activity between the limbs in healthy subjects. The clustering of voxels with high uptake suggests that even in this prolonged repetitive task, different spatial regions of muscles contribute differently to walking than others.

Comparative accuracy of qualitative and quantitative 18F-FDG PET/CT analysis in detection of lymph node metastasis from anal cancer

PURPOSE

To compare the diagnostic performance of qualitative and quantitative 18F-FDG PET/CT in detection of regional and distant lymph node metastasis in patients with anal cancer.

METHODS

Between 2004 and 2017, 28 patients with anal cancer who had staging PET/CT and pathological assessment of suspicious lymph nodes were included. For qualitative analysis, positive lymph nodes were defined as uptake visually higher than the liver reference uptake. For quantitative study, lymph nodes were contoured to determine maximum standard uptake value (SUV_max) and metabolic tumor volume (MTV). Receiver operating characteristic (ROC) curves were plotted to extract the optimal cut-offs and area under the curve (AUC) of SUV_max, lesion to background (L/B) ratio, short axis diameter (SAD), and MTV of lymph nodes. Histopathologic analysis was a reference standard.

RESULTS

A total of 28 lymph nodes (24 inguinal, 2 external iliac, 1 internal iliac, and 1 paraaortic nodes) in 28 patients on PET/CT were included. With the qualitative visual analysis, 19 patients were categorized as positive for nodal metastasis with sensitivity, specificity, and accuracy of 85%, 75%, and 82%. The optimal SUV_max and L/B ratio cut-offs were 2.6 and 1.0 with both sensitivity and specificity of 95% and 75% (AUC of SUV_max = 0.893, AUC of L/B ratio = 0.912). Using the best cut-off of 1.6 cm for SAD and 3.65 cm³ for MTV, both sensitivity and specificity were 80% and 100% (AUC of SAD = 0.950, AUC of MTV = 0.931).

CONCLUSIONS

SUV_max optimization may be helpful in enhancing the diagnostic accuracy of 18F-FDG PET/CT in nodal staging patients with anal cancer.

Characteristic patterns of inter- and intra-hemispheric metabolic connectivity in patients with stable and progressive mild cognitive impairment and Alzheimer's disease

The change in hypometabolism affects the regional links in the brain network. Here, to understand the underlying brain metabolic network deficits during the early stage and disease evolution of AD (Alzheimer disease), we applied correlation analysis to identify the metabolic connectivity patterns using ¹⁸F-FDG PET data for NC (normal control), sMCI (stable MCI), pMCI (progressive MCI) and AD, and explore the inter- and intra-hemispheric connectivity between anatomically-defined brain regions. Regions extracted from 90 anatomical structures were used to construct the matrix for measuring the inter- and intra-hemispheric connectivity. The brain connectivity patterns from the metabolic network show a decreasing trend of inter- and intra-hemispheric connections for NC, sMCI, pMCI and AD. Connection of temporal to the frontal or occipital regions is a characteristic pattern for conversion of NC to MCI, and the density of links in the parietal-occipital network is a differential pattern between sMCI and pMCI. The reduction pattern of inter and intra-hemispheric brain connectivity in the metabolic network depends on the disease stages, and is with a decreasing trend with respect to disease severity. Both frontal-occipital and parietal-occipital connectivity patterns in the metabolic network using ¹⁸F-FDG PET are the key feature for differentiating disease groups in AD.

Comparison of the Variability of SUV Normalized by Skeletal Volume with the Variability of SUV Normalized by Body Weight in 18F-Fluoride PET/CT

Our objective was to test the hypothesis that variability in SUV normalized by skeletal volume (SV) in ¹⁸F-fluoride (¹⁸F-NaF) PET/CT studies is lower than variability in SUV normalized by body weight (BW). Methods: The mean SUV (SUV_mean) was obtained for whole skeletal volume of interest (wsVOI) in 163 selected ¹⁸F-NaF PET/CT studies. These studies were performed to investigate bone metastases and were considered to have normal results. SUV_mean was calculated with normalization by BW (BW SUV_mean), with normalization by SV (SV SUV_mean), and without normalization (WN SUV_mean). The total SV for each patient was also estimated on the basis of the wsVOI defined on the CT component of the PET/CT study. SUV_mean variability for each patient was estimated as the absolute value of the difference between the SUV_mean for the patient and the mean of the SUV_mean for the whole group of patients, divided by the mean of the SUV_mean for the whole group of patients. The variabilities of SUV_mean calculated by the 3 methods were compared using a paired 1-tailed Wilcoxon test. Results: The mean variability for the BW, SV, and WN SUV_mean was 0.16, 0.13, and 0.16, respectively. There were statistically significant differences between SV and BW SUV_mean variability (P = 0.03) and between SV and WN SUV_mean variability (P < 0.01). There was no statistically significant difference between BW and WN SUV_mean variability (P = 0.4). Conclusion: In patients with normal ¹⁸F-NaF PET/CT results, SV SUV_mean presents lower variability than BW SUV_mean.

PET Scan Contribution in Chest Tumor Management: A Systematic Review for Thoracic Surgeons

Aims and background

In the 90s, the introduction of positron emission tomography (PET) represented a milestone in the staging of thoracic tumors. In the last 10 years, PET scan has been widely adopted in thoracic oncology, showing high accuracy in diagnosis and staging and with promising issues in defining prognosis. The aim of this systematic review was to focus on the results and pitfalls of PET scan use in the modern management of chest tumors.

Methods and study design.

The literature search was performed on May 2010 in PubMed, Embase, and Cochrane according to PRISMA protocol. The search was restricted to publications in English, using in the same string the word “PET” with 9 different chest tumors; results were then filtered by eliminating technical articles, focusing only on papers in which surgery was considered as a potential diagnostic or therapeutic tool. From 6600 papers initially selected, 99 manuscripts were fully analyzed.

Results

Glucose uptake is a metabolic marker useful in the diagnosis and staging of chest tumors. In lung cancer screening, standard uptake value is helpful in defining the risk of malignancy of isolated pulmonary nodules. The addition of PET scan to conventional staging increases detection of nodal and distant metastases in lung cancer, esophageal cancer and malignant mesothelioma. In thymoma, a close relationship between standard uptake value, histology, and Masaoka stage has been advocated. This link between glucose uptake and prognosis suggests that PET translates biological tumor behavior into clinically detectable findings.

Conclusions

PET scan has a crucial role in thoracic oncology due to its impact on diagnosis, staging and prognosis. PET scan expresses the biological behavior of tumors, opening interesting perspectives in chest tumor management and improving detection and stage grouping in lung cancer. It anticipates the diagnosis in long-incubating diseases such as mesothelioma and increases biological knowledge of rare diseases, such as thymoma and other mediastinal tumors.

[Basic Evaluation of Standardized Uptake Value Using SPECT Single Unit to Compare with Specific Binding Ratio in Dopamine Transporter Scintigraphy]

Specific binding ratio (SBR) is mainly used as a quantitative index of dopamine transporter scintigraphy, nevertheless, the striatal volume which is influenced by individual differences and aging is calculated as a fixed value. Therefore, standardized uptake value (SUV) calculated with single photon emission computed tomography (SPECT) single unit was compared with SBR. A cylinder phantom filled with Iodine-123 was measured and the calibration factor (CF) was calculated from the count rate per volume. The conditions that SBR calculated using the striatal phantom and the radioactivity concentration calibrated and calculated by CF approximate the actual measured value were determined. There was a strong positive correlation between SBR and SUV with 16 clinical cases in Pearson's correlation coefficient (r>0.7). Moreover, a statistical analysis between the normal and diseased groups for SBR and SUV showed a significant difference (p<0.05). The area under the receiver operating characteristic curve (AUC) of SUV was 0.875, which was useful for clinical diagnosis; however, SBR had a higher diagnostic accuracy. SBR is considered to be suitable for quantitative analysis with SPECT single unit.

Persistent antidepressant effect of low-dose ketamine and activation in the supplementary motor area and anterior cingulate cortex in treatment-resistant depression: A randomized control study

A single low-dose ketamine infusion exhibited a rapid antidepressant effect within 1h. Despite its short biological half-life (approximately 3h), the antidepressant effect of ketamine has been demonstrated to persist for several days. However, changes in brain function responsible for the persistent antidepressant effect of a single low-dose ketamine infusion remain unclear METHODS: Twenty-four patients with treatment-resistant depression (TRD) were randomized into three groups according to the treatment received: 0.5mg/kg ketamine, 0.2mg/kg ketamine, and normal saline infusion. Standardized uptake values (SUVs) of glucose metabolism measured through ¹⁸F-FDG positron-emission-tomography before infusion and 1day after a 40-min ketamine or normal saline infusion were used for subsequent whole-brain voxel-wise analysis and were correlated with depressive symptoms, as defined using the Hamilton Depression Rating Scale-17 (HDRS-17) score RESULTS: The voxel-wise analysis revealed that patients with TRD receiving the 0.5mg/kg ketamine infusion had significantly higher SUVs (corrected for family-wise errors, P = 0.014) in the supplementary motor area (SMA) and dorsal anterior cingulate cortex (dACC) than did those receiving the 0.2mg/kg ketamine infusion. The increase in the SUV in the dACC was negatively correlated with depressive symptoms at 1day after ketamine infusion DISCUSSION: The persistent antidepressant effect of a 0.5mg/kg ketamine infusion may be mediated by increased activation in the SMA and dACC. The higher increase in dACC activation was related to the reduction in depressive symptoms after ketamine infusion. A 0.5mg/kg ketamine infusion facilitated the glutamatergic neurotransmission in the SMA and dACC, which may be responsible for the persistent antidepressant effect of ketamine much beyond its half-life.

PET/MRI: Where might it replace PET/CT?

Simultaneous positron emission tomography and MRI (PET/MRI) is a technology that combines the anatomic and quantitative strengths of MR imaging with physiologic information obtained from PET. PET and computed tomography (PET/CT) performed in a single scanning session is an established technology already in widespread and accepted use worldwide. Given the higher cost and complexity of operating and interpreting the studies obtained on a PET/MRI system, there has been question as to which patients would benefit most from imaging with PET/MRI versus PET/CT. In this article, we compare PET/MRI with PET/CT, detail the applications for which PET/MRI has shown promise and discuss impediments to future adoption. It is our hope that future work will prove the benefit of PET/MRI to specific groups of patients, initially those in which PET/CT and MRI are already performed, leveraging simultaneity and allowing for greater degrees of multiparametric evaluation.

LEVEL OF EVIDENCE

5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2017;46:1247-1262.

FDG uptake in cervical lymph nodes in children without head and neck cancer

BACKGROUND

Reactive cervical lymphadenopathy is common in children and may demonstrate increased ¹⁸F-fluoro-deoxyglucose (¹⁸F-FDG) uptake on positron emission tomography/computed tomography (PET/CT).

OBJECTIVE

We sought to evaluate the frequency and significance of ¹⁸F-FDG uptake by neck lymph nodes in children with no history of head and neck cancer.

MATERIALS AND METHODS

The charts of 244 patients (114 female, mean age: 10.4 years) with a variety of tumors such as lymphoma and post-transplant lymphoproliferative diseases (PTLD), but no head and neck cancers, who had undergone ¹⁸F-FDG PET/CT were reviewed retrospectively. Using the maximum standardized uptake value (SUVmax), increased ¹⁸F-FDG uptake by neck lymph nodes was recorded and compared with the final diagnosis based on follow-up studies or biopsy results.

RESULTS

Neck lymph node uptake was identified in 70/244 (28.6%) of the patients. In 38 patients, the lymph nodes were benign. In eight patients, the lymph nodes were malignant (seven PTLD and one lymphoma). In 24 patients, we were not able to confirm the final diagnosis. Seven out of the eight malignant lymph nodes were positive for PTLD. The mean SUVmax was significantly higher in malignant lesions (4.2) compared with benign lesions (2.1) (P = 0.00049).

CONCLUSION

¹⁸F-FDG uptake in neck lymph nodes is common in children and is frequently due to reactive lymph nodes, especially when the SUVmax is <3.2. The frequency of malignant cervical lymph nodes is higher in PTLD patients compared with other groups.

Prognostic Significance of the Standardized Uptake Value of Pretherapeutic 18F-Labeled 2-Fluoro-2-Deoxyglucose Positron Emission Tomography/Computed Tomography in Patients With Locally Advanced Cervical Cancer

OBJECTIVES

To determine the prognostic significance of the pretreatment and posttreatment maximum standardized uptake value (SUVmax) of F-labeled 2-fluoro-2-deoxyglucose positron emission tomography (PET)/computed tomography imaging in patients with stage IB2-IVA cervical cancer.

METHODS

This was a retrospective review of cervical cancer patients with International Federation of Gynecology and Obstetrics stages IB2-IVA, from March 2008 to April 2014. All patients had pretreatment and posttreatment PET imaging and received primary whole pelvic radiation therapy with concurrent radiosensitizing chemotherapy, followed by intracavitary brachytherapy. Of the 58 patients who met the inclusion criteria, 31 patients (group A) showed no evidence of disease at last follow-up, and 27 patients (group B) presented with recurrence/persistence of disease.

RESULTS

The mean pretreatment SUVmax in group A was 17.65 ± 7.82 versus 18.8 ± 7.77 in group B (P = 0.577). The mean posttreatment SUVmax between the groups was 0.85 ± 1.83 versus 6.05 ± 3.01 (P < 0.001), respectively. The mean difference between pretreatment and posttreatment SUVmax was 17.73 ± 7.50 in group A versus 13.29 ± 7.15 in group B (P = 0.045). In group A, 80.7% of patients demonstrated no posttreatment hypermetabolic activity on PET imaging versus 11.1% in group B. Of the patients who experienced treatment failure, the site of failure was pelvic in 25.9%, distant in 44.4%, and both pelvic and distant in 29.6%.

CONCLUSIONS

No threshold was identified for the pretreatment SUVmax relative to the risk of recurrence. However, distinct correlations were found between the risk of recurrence, percent reduction in SUVmax, and the observation of residual hypermetabolic activity. This finding may help identify candidates for sequential chemotherapy.

SUV Normalized by Skeletal Volume on 18F-Fluoride PET/CT Studies

OBJECTIVE

To propose a technique for SUV normalization on F-fluoride PET/CT (F-NaF) studies based on skeletal volume and to compare the SUVs normalized by this technique with the ones normalized by body weight.

METHODS

SUVs were obtained in volumes of interest (VOIs) in proximal diaphyseal regions of the right humerus (HD) and right femur (FD) in 12 selected F-NaF studies. The 12 studies presented both regions considered normal by visual examination on PET and CT and were performed in patients presenting body weight below 50 kg (B50) or above 90 kg (A90) (6 patients in each group). The maximum SUVs were calculated in these 2 bone regions in both groups of patients using body weight (SUV BW) and skeletal volume (SUV SV) methodologies. The total skeletal volume for each patient was estimated based on whole skeletal VOIs automatically defined on the CT component of the PET/CT study. The maximum SUVs calculated using the 2 methodologies were compared.

RESULTS

The maximum SUVs BW were statistically higher in the group A90 in both regions, with a P < 0.001 and P < 0.008 for FD and HD, respectively. The maximum SUVs SV in the 2 regions were not statistically different between the groups B50 and A90, P values of 0.27 and 0.87 for FD and HD, respectively.

CONCLUSIONS

The SUVs normalized by skeletal volume present similar results in groups of patients with extremes of body weight. Therefore, this methodology could be more adequate than the one normalized by body weight to semiquantitatively analyze F-NaF studies.

Hypothalamic AMP-Activated Protein Kinase Regulates Biphasic Insulin Secretion from Pancreatic β Cells during Fasting and in Type 2 Diabetes

Glucose-stimulated insulin secretion (GSIS) by pancreatic β cells is biphasic. However, the physiological significance of biphasic GSIS and its relationship to diabetes are not yet fully understood. This study demonstrated that impaired first-phase GSIS follows fasting, leading to increased blood glucose levels and brain glucose distribution in humans. Animal experiments to determine a possible network between the brain and β cells revealed that fasting-dependent hyperactivation of AMP-activated protein kinase in the hypothalamus inhibited first-phase GSIS by stimulating the α-adrenergic pancreatic nerve. Furthermore, abnormal excitability of this brain-β cell neural axis was involved in diabetes-related impairment of first-phase GSIS in diabetic animals. Finally, pancreatic denervation improved first-phase GSIS and glucose tolerance and ameliorated severe diabetes by preventing β cell loss in diabetic animals. These results indicate that impaired first-phase GSIS is critical for brain distribution of dietary glucose after fasting. Furthermore, β cells in individuals with diabetes mistakenly sense that they are under conditions that mimic prolonged fasting. The present study provides additional insight into both β cell physiology and the pathogenesis of β cell dysfunction in type 2 diabetes.

•

Fasting-induced hypothalamic AMPK activation inhibited first-phase GSIS by stimulating the α-adrenergic nerve.

•

The brain-pancreas neural axis was involved in β cell dysfunction and glucose intolerance in diabetes.

•

Pancreatic denervation improved first-phase GSIS, glucose tolerance and β cell survival in type 2 diabetic animals.

Glucose-stimulated insulin secretion (GSIS) from pancreatic β cells is biphasic. Furthermore, first-phase GSIS is inhibited in type 2 diabetes. This study revealed that fasting reduced first-phase GSIS by signaling via the brain-pancreatic β cell neural axis, which is essential for maintaining glucose supply to the brain at re-feeding after fasting. Abnormal excitability of this neural axis was also associated with impaired first-phase GSIS in type 2 diabetes. Surgical pancreatic denervation improved diabetes in an animal study. The present data reveal that diabetic β cells exist under conditions that mimic starvation and provide a therapeutic potency of pancreatic denervation against diabetes.

DICOM for quantitative imaging biomarker development: a standards based approach to sharing clinical data and structured PET/CT analysis results in head and neck cancer research

Background. Imaging biomarkers hold tremendous promise for precision medicine clinical applications. Development of such biomarkers relies heavily on image post-processing tools for automated image quantitation. Their deployment in the context of clinical research necessitates interoperability with the clinical systems. Comparison with the established outcomes and evaluation tasks motivate integration of the clinical and imaging data, and the use of standardized approaches to support annotation and sharing of the analysis results and semantics. We developed the methodology and tools to support these tasks in Positron Emission Tomography and Computed Tomography (PET/CT) quantitative imaging (QI) biomarker development applied to head and neck cancer (HNC) treatment response assessment, using the Digital Imaging and Communications in Medicine (DICOM(®)) international standard and free open-source software. Methods. Quantitative analysis of PET/CT imaging data collected on patients undergoing treatment for HNC was conducted. Processing steps included Standardized Uptake Value (SUV) normalization of the images, segmentation of the tumor using manual and semi-automatic approaches, automatic segmentation of the reference regions, and extraction of the volumetric segmentation-based measurements. Suitable components of the DICOM standard were identified to model the various types of data produced by the analysis. A developer toolkit of conversion routines and an Application Programming Interface (API) were contributed and applied to create a standards-based representation of the data. Results. DICOM Real World Value Mapping, Segmentation and Structured Reporting objects were utilized for standards-compliant representation of the PET/CT QI analysis results and relevant clinical data. A number of correction proposals to the standard were developed. The open-source DICOM toolkit (DCMTK) was improved to simplify the task of DICOM encoding by introducing new API abstractions. Conversion and visualization tools utilizing this toolkit were developed. The encoded objects were validated for consistency and interoperability. The resulting dataset was deposited in the QIN-HEADNECK collection of The Cancer Imaging Archive (TCIA). Supporting tools for data analysis and DICOM conversion were made available as free open-source software. Discussion. We presented a detailed investigation of the development and application of the DICOM model, as well as the supporting open-source tools and toolkits, to accommodate representation of the research data in QI biomarker development. We demonstrated that the DICOM standard can be used to represent the types of data relevant in HNC QI biomarker development, and encode their complex relationships. The resulting annotated objects are amenable to data mining applications, and are interoperable with a variety of systems that support the DICOM standard.

Positron Emission Tomography

Positron emission tomography (PET) is a minimally invasive imaging procedure with a wide range of clinical and research applications. PET allows for the three-dimensional mapping of administered positron-emitting radiopharmaceuticals such as (18)F-fluorodeoxyglucose (for imaging glucose metabolism). PET enables the study of biologic function in both health and disease, in contrast to magnetic resonance imaging (MRI) and computed tomography (CT), that are more suited to study a body's morphologic changes, although functional MRI can also be used to study certain brain functions by measuring blood flow changes during task performance. This chapter first provides an overview of the basic physics principles and instrumentation behind PET methodology, with an introduction to the merits of merging functional PET imaging with anatomic CT or MRI imaging. We then focus on clinical neurologic disorders, and reference research on relevant PET radiopharmaceuticals when applicable. We then provide an overview of PET scan interpretation and findings in several specific neurologic disorders such as dementias, epilepsy, movement disorders, infection, cerebrovascular disorders, and brain tumors.

Do 18F-FDG PET/CT parameters in oropharyngeal and oral cavity squamous cell carcinomas indicate HPV status?

OBJECTIVE

The aim of this study was to explore the relationship of PET/CT parameters with human papillomavirus (HPV) status of oropharyngeal (OP) and oral cavity (OC) squamous cell carcinomas (SCCs).

PATIENTS AND METHODS

We retrospectively reviewed 39 patients with OC and OP-SCC who underwent staging 18F-FDG PET/CT. PET/CT parameters were measured for the primary tumor and the hottest involved node, including SUV max, SUV mean, SUV peak, metabolic tumor volume, total lesion glycolysis, standardized added metabolic activity (SAM), and normalized SAM. Patient characteristics were compared between HPV positive (HPV+) and negative (HPV-) groups. Receiver operating characteristic analysis was used to dichotomize PET/CT parameters into high and low. Logistic regression models predicting HPV status were fit for each PET/CT parameter.

RESULTS

The HPV+ group was composed of 18 patients all with OP-SCC; the HPV- group consisted of 21 patients, 4 OP cancer patients and 17 OC cancer patients. The HPV+ group had a higher proportion of N2 stage (94% vs 43%; P < 0.001). Nodal PET/CT parameters were higher in the HPV+ group (P < 0.01); this difference was not present for the primary lesion. After adjusting for sex and age, the association of higher nodal SUV max (odds ratio [OR], 9.67), SUV mean (OR, 10.48), SUV peak (OR 9.67), metabolic tumor volume (OR, 14.52), total lesion glycolysis (OR, 11.84), and SAM, normalized SAM (OR, 16.21) with HPV+ status remained statistically significant (P < 0.05).

CONCLUSIONS

Nodal PET/CT parameters predict HPV status. High nodal FDG uptake should raise suspicion for positive HPV status in the evaluation of the primary lesion.

Standardized uptake value and apparent diffusion coefficient of endometrial cancer evaluated with integrated whole-body PET/MR: Correlation with pathological prognostic factors

PURPOSE

To evaluate the correlation between maximum standardized uptake value (SUVmax ) and minimum apparent diffusion coefficient (ADCmin ) of endometrial cancer derived from an integrated positron emission tomography / magnetic resonance (PET/MR) system and to determine their correlation with pathological prognostic factors.

MATERIALS AND METHODS

This prospective study was approved by the Institutional Review Board of the hospital, and informed consent was obtained. Between April and December 2014, 47 consecutive patients with endometrial cancer were enrolled and underwent simultaneous PET/MR examinations before surgery. Thirty-six patients with measurable tumors on PET/MR were included for image analysis. Pearson's correlation coefficient was used to evaluate the correlation between SUVmax and ADCmin of the tumors. The Mann-Whitney U-test was utilized to evaluate relationships between these two imaging biomarkers and pathological prognostic factors.

RESULTS

The mean SUVmax and ADCmin were 14.7 ± 7.1 and 0.48 ± 0.13 × 10(-3) mm(2) /s, respectively. A significant inverse correlation was found between SUVmax and ADCmin (r = -0.53; P = 0.001). SUVmax was significantly higher in tumors with advanced stage, deep myometrial invasion, cervical invasion, lymphovascular space involvement, and lymph node metastasis (P < 0.05). ADCmin was lower in tumors with higher grade, advanced stage, and cervical invasion (P < 0.05). The ratio of SUVmax to ADCmin was higher in tumors with higher grade, advanced stage, deep myometrial invasion, cervical invasion, lymphovascular space involvement, and lymph node metastasis (P < 0.05).

CONCLUSION

SUVmax and ADCmin of endometrial cancer derived from integrated PET/MR are inversely correlated and are associated with pathological prognostic factors.

High-resolution(18)F-fluorodeoxyglucose positron emission tomography and magnetic resonance imaging for pituitary adenoma detection in Cushing disease

OBJECT High-resolution PET (hrPET) performed using a high-resolution research tomograph is reported as having a resolution of 2 mm and could be used to detect corticotroph adenomas through uptake of(18)F-fluorodeoxyglucose ((18)F-FDG). To determine the sensitivity of this imaging modality, the authors compared(18)F-FDG hrPET and MRI detection of pituitary adenomas in Cushing disease (CD). METHODS Consecutive patients with CD who underwent preoperative(18)F-FDG hrPET and MRI (spin echo [SE] and spoiled gradient recalled [SPGR] sequences) were prospectively analyzed. Standardized uptake values (SUVs) were calculated from hrPET and were compared with MRI findings. Imaging findings were correlated to operative and histological findings. RESULTS Ten patients (7 females and 3 males) were included (mean age 30.8 ± 19.3 years; range 11-59 years). MRI revealed a pituitary adenoma in 4 patients (40% of patients) on SE and 7 patients (70%) on SPGR sequences.(18)F-FDG hrPET demonstrated increased(18)F-FDG uptake consistent with an adenoma in 4 patients (40%; adenoma size range 3-14 mm). Maximum SUV was significantly higher for(18)F-FDG hrPET-positive tumors (difference = 5.1, 95% CI 2.1-8.1; p = 0.004) than for(18)F-FDG hrPET-negative tumors.(18)F-FDG hrPET positivity was not associated with tumor volume (p = 0.2) or dural invasion (p = 0.5). Midnight and morning ACTH levels were associated with(18)F-FDG hrPET positivity (p = 0.01 and 0.04, respectively) and correlated with the maximum SUV (R = 0.9; p = 0.001) and average SUV (R = 0.8; p = 0.01). All(18)F-FDG hrPET-positive adenomas had a less than a 180% ACTH increase and(18)F-FDG hrPET-negative adenomas had a greater than 180% ACTH increase after CRH stimulation (p = 0.03). Three adenomas were detected on SPGR MRI sequences that were not detected by(18)F-FDG hrPET imaging. Two adenomas not detected on SE (but no adenomas not detected on SPGR) were detected on(18)F-FDG hrPET. CONCLUSIONS While(18)F-FDG hrPET imaging can detect small functioning corticotroph adenomas and is more sensitive than SE MRI, SPGR MRI is more sensitive than(18)F-FDG hrPET and SE MRI in the detection of CD-associated pituitary adenomas. Response to CRH stimulation can predict(18)F-FDG hrPET-positive adenomas in CD.

A computational framework for cancer response assessment based on oncological PET-CT scans

In this work we present a comprehensive computational framework to help in the clinical assessment of cancer response from a pair of time consecutive oncological PET-CT scans. In this scenario, the design and implementation of a supervised machine learning system to predict and quantify cancer progression or response conditions by introducing a novel feature set that models the underlying clinical context is described. Performance results in 100 clinical cases (corresponding to 200 whole body PET-CT scans) in comparing expert-based visual analysis and classifier decision making show up to 70% accuracy within a completely automatic pipeline and 90% accuracy when providing the system with expert-guided PET tumor segmentation masks.